Tuesday 10 January 2012 14.59 EST
First published on Tuesday 10 January 2012 14.59 EST

As anyone who has paid due attention to the televised advice of Tyra Banks will know, models smile with their eyes. They do not, as a general rule, smile with their mouths. And certainly not with their teeth. But that is exactly what Arizona Muse is doing on the front cover of this month's Vogue, a wide-mouthed smile outlined with such deeply stained lips, it looks as if the makeup artist has ringed her teeth with red marker: yes, those really are the things to note. It is also what Kate Middleton is doing on the front of Tatler. Ditto Reese Witherspoon (though without the teeth) on Marie Claire.

And models are smiling at us not just from front covers but inside pages, too: there is Audrey Tautou with a serene, private smile for Chanel No 5, Liya Kebede open-mouthed and toothy for luxury brand Bottega Veneta, Lindsey Wixson and Frida Gustavsson in hysterics at Mulberry. At Bally they are giggling, their cheeks in creases, while feeding a couple of goats (well, that is funny). The Clarks women are captivated by something hilarious just out of shot. What is going on?

"Smiling – doesn't cost anything? Does it?" says Vogue editor Alexandra Shulman in reply to an enquiry. "There's so much bad news around. I imagine a lot of people have thought similarly, that anything you can do to dispel the glums is welcome."

This is not the first time in recent history that fashion has shone upon the smile. As Alice Rawsthorn, design critic of the International Herald Tribune, points out: "The honourable exception to the general glumness of fashion photography is i-D with its long tradition of 'winking' cover stars." And every now and then a designer goes rogue and sends models down the runway with the corners of their mouths turned up: Anna Sui in October 2008, Stella McCartney in March 2009, Michael Kors last autumn. But the smile, it seems, doesn't last. So why is this happening now?

"It's an instinctive desire from designers to connect with the consumer," says fashion commentator Caryn Franklin. "Because the default setting for the model pose is preoccupied: 'I'm too cool to be here.' Recessionary posing means cheering people up. It's a route to profit. But it made you feel more included, didn't it?"

Actually, it did change the reading experience. It was certainly pretty jolly at first, but after a while I started wondering what they were all smiling at. Had I done something embarrassing that they could see? It was a bit like those childhood nightmares when all your dolls come to life, or when an arm reaches out of the mirror.

Still, on the plus side, this is a fashion you can wear for free (memo: must book dentist appointment), and that suits me.